Apparatus and method for making carbon nanotube film

ABSTRACT

An apparatus for making a carbon nanotube film includes a substrate holder, a bar supplying device, a carrier device, and a stretching device arranged in alignment in that order. A method for making a carbon nanotube film is further provided.

BACKGROUND

1. Field of the Invention

The present invention relates to an apparatus and method for makingcarbon nanotube film.

2. Discussion of Related Art

Carbon nanotubes (CNTs) are a novel carbonaceous material and havereceived a great deal of interest since the early 1990s. Carbonnanotubes have interesting and potentially useful electrical andmechanical properties. Due to these and other properties, CNTs havebecome an important new material for use in a variety of fields.However, the acquired CNTs are generally in a form of particles orpowder and that is inconvenient for applications. So it is necessary tomake carbon nanotube film.

Nowadays, methods for making carbon nanotube film include, usingchemical vapor deposition (CVD) to grow a carbon nanotube film bydissolving carbon nanotube powder into a solvent to form a solution,coating the solution onto a surface of a substrate, and drying thesolution thereon to form a carbon nanotube film. There is also theLangmuir Blodgett (LB) method, which involves mixing the carbon nanotubesolution with another solution having a different density, causing thecarbon nanotubes to float on the surface of the solution to form acarbon nanotube film. The carbon nanotube film acquired by the LB methodis a uniform net structure and the carbon nanotubes in the carbonnanotube film are dispersed uniformly and without agglomeration. But thecarbon nanotubes in the carbon nanotube film are disordered and notconducive to exploitation.

What's more, the aforementioned methods for making carbon nanotube filmare limited to laboratory use, and so are not suitable for use in a massproduction setting.

What is needed, therefore, is an apparatus and a method for making thecarbon nanotube film, the apparatus being easy to manipulate, and themethod being conducive to mass production, and the carbon nanotubes inthe carbon nanotube film are dispersed uniformly and arranged in apreferred orientation.

SUMMARY

In one embodiment, an apparatus for making a carbon nanotube filmincludes a substrate holder, a bar supplying device, a carrier device,and a stretching device arranged in alignment in that order.

Other advantages and novel features of the present apparatus and methodfor making a carbon nanotube film will become more apparent from thefollowing detailed description of preferred embodiments when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present apparatus and method for making the carbonnanotube film can be better understood with reference to the followingdrawings. The components in the drawings are not necessarily to scale,the emphasis instead being placed upon clearly illustrating theprinciples of the present apparatus and method for making the carbonnanotube film.

FIG. 1 is a schematic view of an apparatus for making a carbon nanotubefilm.

FIG. 2 is flow chart of a method for making a carbon nanotube film usingthe apparatus of FIG. 1.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate at least one preferred embodiment of the present apparatusand method for making the carbon nanotube film, in at least one form,and such exemplifications are not to be construed as limiting the scopeof the invention in any manner.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made to the drawings to describe, in detail,embodiments of the present apparatus and method for making the carbonnanotube film.

Referring to FIG. 1, an apparatus 100 for making a carbon nanotube filmincludes a substrate holder 110, a bar supplying device 120, a carrierdevice 130, and a stretching device 140 arranged in alignment in thatorder.

The substrate holder 110 is a fixed device for supporting a substrate.The substrate holder 110 has a planer surface 112, and the substratewith a carbon nanotube array 116 formed thereon, can be fixed, such aswith an adhesive, on the planer surface 112 of the substrate holder 110.A carbon nanotube film 118 with a predetermined length can be drawn fromthe carbon nanotube array 116 by a drawing tool.

The bar supply device 120 has a supply stage 122. Bars are placed on thesurface of the supply stage 122 of the bar supply device 120. The barsare strip-shaped or cube-shaped. The supply stage 122 is keptcontinuously supplied with bars during production of the carbon nanotubefilm. The material of the bars can be selected from a group consistingof metal, glass, rubber and plastic. Beneficially, the material of thebars is metal in the present embodiment. The length of each bar isgreater than the width of the carbon nanotube film 118. The supplydevice 120 and the supply stage 122 can be raised or lowered eithermanually or by computer control.

The carrier device 130 includes a carrier stage 132. The carrier stage132 can be rotated about a central axis thereof perpendicular to theface of the carrier stage 132, and can also be raised or lowered viacomputer control. In operation, a supporting element 134 is disposed onthe carrier stage 132 for collecting and supporting the carbon nanotubefilms prepared by the apparatus 100.

The stretching device 140 includes a fixing device 142. The fixingdevice 142 can be a generally U-shaped clamp with an adjustable openingfacing the carbon nanotube array 116. The stretching device 140 isconfigured to move to the supply stage 122, and then the fixing device142 is controlled to seize a bar by the ends thereof and then thestretching device 140 moves away from the supply stage 122 and thesubstrate holder 110. The fixing device 142 can be controlled to move upand down and side to side to control the drawing of the carbon nanotubefilm. The direction and the speed of the movement of the fixing device142 can be adjusted via the computer. In operation, the fixing device142 can clamp the two ends of a first bar 124 and, with the carbonnanotube film 118 attached to the bar 124, the stretching device 140moves back, stretch the carbon nanotube film 118 along the drawingdirection thereof.

Referring to FIG. 2, a method for making a carbon nanotube film usingthe apparatus 100 includes the following steps of: (a) providing thecarbon nanotube array 116 on the substrate 114, and fixing the substrate114 with the carbon nanotube array 116 thereon to the substrate holder110; (b) drawing the carbon nanotube film 118 with a predeterminedlength from the carbon nanotube array 116 by a drawing tool, adheringone end of the carbon nanotube film 118 to the first bar 124 on thesupply stage 122 of the bar supply device 120; (c) fixing the first bar124 to the stretching device 140, and stretching the carbon nanotubefilm via pulling the first bar 124 by the stretching device 140 for acertain length; (d) supplying a second bar 126 on the supply stage 122of the bar supply device 120, and adhering a part of the carbon nanotubefilm 118 above the second bar 126 to the second bar 126; (e) providing asupporting element 134 on the carrier stage 132, and adhering a part ofthe carbon nanotube film 118 between the first bar 124 and the secondbar 126 to the supporting element 134; and (f) cutting the carbonnanotube film 118 between the first bar 124 and the supporting element134 and between the second bar 126 and the supporting element 134respectively to acquire the carbon nanotube film 118 on the supportingelement 134.

In step (a), the carbon nanotube array 116 is a super-aligned array ofcarbon nanotubes. The super-aligned array of carbon nanotubes can beformed by the steps of: (a1) providing a substantially flat and smoothsubstrate 114; (a2) forming a catalyst layer on the substrate 114; (a3)annealing the substrate 114 with the catalyst layer thereon in air at atemperature in an approximate range from 700° C. to 900° C. for about 30to 90 minutes; (a4) heating the substrate 114 with the catalyst layerthereon at a temperature in an approximate range from 500° C. to 740° C.in a furnace with a protective gas therein; and (a5) supplying a carbonsource gas to the furnace for about 5 to 30 minutes and growing asuper-aligned array of carbon nanotubes on the substrate.

In step (a1), the substrate 114 can be a P-type silicon wafer, an N-typesilicon wafer, or a silicon wafer with a film of silicon dioxidethereon. Preferably, a 4 inch P-type silicon wafer is used as thesubstrate. In step (a2), the catalyst can, advantageously, be made ofiron (Fe), cobalt (Co), nickel (Ni), or any alloy thereof.

In step (a4), the protective gas can, beneficially, be made up of atleast one of nitrogen (N₂), ammonia (NH₃), and a noble gas. In step(a5), the carbon source gas can be a hydrocarbon gas, such as ethylene(C₂H₄), methane (CH₄), acetylene (C₂H₂), ethane (C₂H₆), or anycombination thereof.

The super-aligned array of carbon nanotubes can, opportunely, have aheight of about 200 to 400 microns and includes a plurality of carbonnanotubes parallel to each other and approximately perpendicular to thesubstrate. The super-aligned array of carbon nanotubes formed under theabove conditions is essentially free of impurities, such as carbonaceousor residual catalyst particles. The carbon nanotubes in thesuper-aligned array are closely packed together by the van der Waalsattractive force.

In step (a), the substrate 114 and the carbon nanotube array 116 can befixed on a substrate holder 110 via adhesive or adhesive tape.

Step (b) further includes the substeps of: (b1) selecting a plurality ofcarbon nanotube segments having a predetermined width from the array ofcarbon nanotubes; (b2) pulling the carbon nanotube segments at aneven/uniform speed to form the carbon nanotube film 118.

In step (b1), quite usefully, the carbon nanotube segments having apredetermined width can be selected by using an adhesive tape as a toolto contact with the super-aligned array. In step (b2), an angle betweenthe direction of stretching the carbon nanotube film and the growingdirection of the carbon nanotube array 114 is in an approximate rangefrom 30° to 90°. Beneficially, the stretching direction is substantiallyperpendicular to the growing direction of the carbon nanotube array 114.The height of the bar supply device 120 can be adjusted to make thebottom surface of the carbon nanotube film 118 contact with and adhereto the first bar 124 supplied by the bar supply device 120 to keep thecarbon nanotube film 118 stretched.

More specifically, during the pulling process, as the initial carbonnanotube segments are drawn out, other carbon nanotube segments are alsodrawn out end to end, due to the van der Waals attractive force betweenends of adjacent segments. The carbon nanotube film 118 produced in suchmanner can be selectively formed having a predetermined width. Thecarbon nanotube film 118 includes a plurality of carbon nanotubesegments. The carbon nanotubes in the carbon nanotube film 118 aremainly parallel to the pulling direction of the carbon nanotube film118.

A width of the carbon nanotube film 118 depends on a size of the carbonnanotube array 114. A length of the carbon nanotube film 118 can bearbitrarily set as desired. In one useful embodiment, when the substrate114 is a 4 inch type wafer as in the present embodiment, a width of thecarbon nanotube film 118 is in an approximate range from 1 centimeter to10 centimeters. The thickness of the carbon nanotube film 118 is in anapproximate range from 10 nanometers to 100 micrometers.

It is noted that because the carbon nanotubes in the super-alignedcarbon nanotube array have a high purity and a high specific surfacearea, the carbon nanotube film 118 is adhesive. As such, the carbonnanotube film 118 can be adhered to the surface of the bars directly.

In step (c), the length of the carbon nanotube film is longer than thedistance between the substrate 114 and the supporting element 134. Step(c) includes the substeps of: (c1) moving the fixing device 142 of thestretching device 140 close to the first bar 124; (c2) seizing of thefirst bar 124 by the fixing device 142; (c3) adjusting the stretchingdevice 140 to stretch the carbon nanotube film 118 via pulling the firstbar 124 along a direction perpendicular to the growing direction of thecarbon nanotube array 114 and stretching the carbon nanotube film 118for a certain length to make a part of the carbon nanotube film 118being disposed above the carrier stage 132.

In the present embodiment, the fixing device 142 can generally be aU-shaped clamp with an opening facing the carbon nanotube array 116. Thewidth of the opening of the fixing device 142 can be adjusted. Step (c2)can be executed by moving the fixing device 142 near to the first bar124, the first bar 124 being disposed at the opening of the U-shapedclamp, and adjusting the width of the opening to clamp the two ends ofthe bar 124 via the U-shaped clamp and fixing the first bar 124 on thestretching device 140.

In step (d), a part of the carbon nanotube film 118 between the firstbar 124 and the second bar 126 is hung. In step (e), the supportingelement 134 having a predetermined shape can be a material supportingthe carbon nanotube film and the supporting element 134 can be asubstrate or a frame. In the present embodiment, the supporting element134 is a square substrate. The material of the supporting element 134can be any material, such as metal, plastic glass, or rubber.Beneficially, the material of the supporting element 134 is metal.

Step (e) includes the substeps of: (e1) placing the supporting element134 on the carrier stage 132 of the carrier device 130; (e2) adjustingthe position of the carrier stage 132 to position the supporting element134 below the carbon nanotube film 118 between the first bar 124 and thesecond bar 126; (e3) adjusting the height of the carrier stage 132 ofthe carrier device 130 and the height of the fixing device 142 tocontact the bottom surface of a part of the carbon nanotube film 118above the supporting element 134 with the supporting element 134 and thecarbon nanotube film 118 being adhered thereon.

In step (f), when a part of the carbon nanotube film 118 is on thesupporting element 134, the other part of the carbon nanotube film 118stretched by the second bar 126 is kept in a state of stretching.Repeating step (c), step (d), step (e) and step (0, and a plurality ofcarbon nanotube films 118 can be accumulated on the supporting element134 and the angle between the aligned direction of the adjacent twolayers of carbon nanotube films 118 can be adjusted via rotating thecarrier stage 132 in a horizontal surface. The carbon nanotube films 118overlaps each other to form a multi-layer carbon nanotube filmstructure.

A method for making the multi-layer carbon nanotube film structureincludes the steps of: (g) fixing the second bar 126 on the stretchingdevice 140, stretching the carbon nanotube film 118 via pulling thesecond bar 126 by the stretching device 140 for a certain length; (h)supplying a third bar on the supply stage 122 of the bar supply device120 and adhering a part of the carbon nanotube film 118, above the thirdbar, to the third bar; (i) adjusting the height of the supportingelement 134 and adhering the carbon nanotube film 118 between the secondbar 124 and the third bar on the supporting element 134; and (j) cuttingthe carbon nanotube film 118 between the second bar 124 and thesupporting element 134 and between the third bar and the supportingelement 134 respectively to acquire another carbon nanotube film 118 onthe supporting element 134. Repeating step (g), step (h), step (i) andstep (j), and a multi-layer carbon nanotube film structure can beacquired on the same supporting element 134. It can be understood thatreplacing the supporting element 134, a plurality of carbon nanotubefilms 118 can be acquired.

Compared to the conventional apparatus and method for making carbonnanotube film, the present apparatus and method for making carbonnanotube film have the following virtues: firstly, the apparatus is easyto be manipulated and can realize semi-automatic continuous productionand mass production via being controlled by computer; secondly, thecarbon nanotubes in the carbon nanotube film drawn directly from thecarbon nanotube array has a uniform distribution therein and arearranged in a preferred orientation.

Finally, it is to be understood that the above-described embodiments areintended to illustrate rather than limit the invention. Variations maybe made to the embodiments without departing from the spirit of theinvention as claimed. The above-described embodiments illustrate thescope of the invention but do not restrict the scope of the invention.

1. An apparatus for making a carbon nanotube film, comprising: a substrate holder, a bar supplying device, a carrier device, and a stretching device arranged in alignment in that order.
 2. The apparatus as claimed in claim 1, wherein the substrate holder has a planar surface, and a substrate with a carbon nanotube array formed thereon can be fixed on the planer surface thereof.
 3. The apparatus as claimed in claim 1, wherein the bar supplying device can be raised and lowered.
 4. The apparatus as claimed in claim 1, wherein the bar supplying device has a supply stage with bars placed on the surface thereof.
 5. The apparatus as claimed in claim 1, wherein the carrier device has a carrier stage with a supporting element placed on the surface thereof.
 6. The apparatus as claimed in claim 5, wherein the carrier stage can be rotated about a central axis thereof perpendicular to surface of the carrier stage.
 7. The apparatus as claimed in claim 5, wherein the carrier stage can be controlled to move up and down and side to side.
 8. The apparatus as claimed in claim 1, wherein the stretching device has a fixing device.
 9. The apparatus as claimed in claim 8, wherein the fixing device can be controlled to move up and down and side to side.
 10. A method for making a carbon nanotube film, comprising the following steps of: (a) providing the carbon nanotube array on a substrate, and fixing the substrate with the carbon nanotube array thereon to the substrate holder; (b) drawing the carbon nanotube film with a predetermined length from the carbon nanotube array by a drawing tool, adhering one end of the carbon nanotube film to the first bar on the supply stage of the bar supply device; (c) fixing the first bar to the stretching device, and stretching the carbon nanotube film via pulling the first bar by the stretching device for a certain length; (d) supplying a second bar on the supply stage of the bar supply device, and adhering a part of the carbon nanotube film, above the second bar, to the second bar; (e) providing a supporting element on the carrier stage, and adhering a part of the carbon nanotube film, between the first bar and the second bar, to the supporting element; and (f) cutting the carbon nanotube film between the first bar and the supporting element and between the second bar and the supporting element respectively to acquire the carbon nanotube film on the supporting element.
 11. The method as claimed in claim 10, further comprising the following steps of: (g) fixing the second bar to the stretching device, stretching the carbon nanotube film by the stretching device via pulling the second bar by the stretching device for a certain length; (h) supplying a third bar on the supply stage of the bar supply device and adhering a part of the carbon nanotube film above the third bar to the third bar; (i) adjusting the height of the supporting element and adhering the carbon nanotube film between the second bar and the third bar to the supporting element; and (j) cutting the carbon nanotube film between the second bar and the supporting element and between the third bar and the supporting element respectively to acquire another carbon nanotube film on the supporting element.
 12. The method as claimed in claim 10, wherein the carbon nanotube array is a super-aligned carbon nanotube array.
 13. The method as claimed in claim 10, wherein the material of the first bar and the second bar can be selected from a group consisting of metal, glass, rubber and plastic.
 14. The method as claimed in claim 10, wherein the supporting element is a substrate or a frame.
 15. The method as claimed in claim 10, wherein the material of the supporting element can be selected from a group consisting of metal, glass, rubber and plastic.
 16. The method as claimed in claim 10, wherein an angle between the direction of stretching the carbon nanotube film and the growing direction of the carbon nanotube array is in an approximate range from 30° to 90°. 